The conventional ultrasonic resonators are designed to produce intensive longitudinal vibration, as represented by Langevin type on. On the other hand, there have recently been developed techniques to utilize strong rotation torque by ultrasonic vibration such as as in ultrasonic motor, ultrasonic parts feeder, etc.
While there have been proposed various methods of generating rotary torque, it is considered most superior to take a method of producing an elliptical vibrational motion on the surface of the stator of the motor and rotating the rotor which is accommodated under pressure contact thereto. Although it is convenient if the vibrating surface of the ultrasonic resonator can be directly utilized as a stator, it was not possible to find a method of efficiently generating the intensive elliptical vibrational motion on the surface of one ultrasonic resonator, and it was necessary to combine plural resonators and only the inefficient and low vibration could be generated, so that the practical utility was insufficient.